r14451: In order to get pdb_ldap searching for SID_NAME_ALIAS

r14451: In order to get pdb_ldap searching for SID_NAME_ALIAS
groups in the ${MACHINESID} and S_1-5-32 domains correctly,
I had to add a substr search on sambaSID.

* add substr matching rule to OpenLDAP schema
  (we need to update the other schema as will since this
  is a pretty important change).  Sites will need to
  - install the new schema
  - add 'indea sambaSID   sub' to slapd.conf
  - run slapindex

* remove uses of SID_NAME_WKN_GRP in pdb_ldap.c
(This used to be commit 2c0a46d73122e9000a900f7e16f9b010ad4b78e3)